7:33 p.m. ET: Singer Willie Nelson has pledged his proceeds from his previously scheduled performance at The Backyard in Austin, Texas on April 28 to go to the West Volunteer Fire Department.

"West is just a few miles from my hometown of Abbott. I was born and raised here and it was my backyard growing up. This is my community. These friends and neighbors have always been and are still a part of my life. My heart is praying for the community that we call home," Nelson said in a statement.

6:19 p.m. ET: A Real Role Model - Captain Harris

"Captain Harris' response is typical of all our first responders; night and day, no matter where they are, no matter if they are on or off duty they respond with the greatest acts of bravery," said City Manager Mary K. Suhm in a statement. "The City of Dallas and the citizens of Dallas have lost a real role model."

Dallas Fire Dept

6:10 p.m. ET: A Dallas Fire-Rescue Captain was killed in the explosion, according to a news release from Dallas city officials. Captain Kenny Harris was first reported missing following Wednesday's blast. Harris was a West resident and was off-duty at the time of the incident.

"Captain Harris rushed to the scene compelled to provide assistance to his community during this crisis," said Mayor Mike Rawlings in a statement. "I want to express my deepest condolences to his family, friends and co-workers," he said.

"Our hearts are heavy and hurting with the loss of such a great firefighter, great husband and great family man. Dallas Fire-Rescue is wrapping its arms around the Harris family to provide comfort and support," said Dallas Fire Chief Louie Bright III.

4:55 p.m. ET: Officer Jason Reyes at Texas Department of Public Safety said at a press conference that officials were no longer estimating the number of fatalities, which was confirmed earlier as between five and 15. Reyes said that they would say only that there were confirmed causalities.

Texas Attorney General Greg Abbott told reporters that the state of Texas would provide whatever resources were needed to the victims in west.

"Literally in an instant, these families have been ripped apart," Abbott said. "These lives in this community will be put back together."

Abbott also issued a stern warning to anyone in the area caught price-gouging.

"It seems like when tragedies arise, they are followed by price gouging," he said. "My office has declared a warning in regard to price gouging. If anyone tried to profit off this tragedy, they will be facing the wrong end of a lawsuit from the Texas attorney general."

3:35 p.m. ET: The Environmental Protection Agency conducted an inspection of the Risk Management Plan (RMP) at the plant on March 16, 2006. The agency told ABCNews.com that a number of deficiencies were found, and the plant was fined $2,300.

The deficiencies identified by inspectors in 2006 included:

Failure to update its RMP in a timely manner. The update was due in 2004, but wasn't updated until 2006

Failure to document that hazards identified in the hazard review had been addressed

2:45 p.m. ET: Texas officials will not talk about what may have caused the massive explosion, but Nim Kidd with Texas Emergency Management said that on site at the West Fertilizer Plant were tanks holding anhydrous ammonia, which can be kept as a liquid under pressure.

Anhydrous ammonia is a toxic liquid that, when concentrated, is corrosive to tissues upon contact, according to the Center for Disease Control and Prevention.

Also on site at the West Fertilizer Plant was ammonium nitrate, which is a solid product.

"A lot of people don't like putting water and ammonium nitrate together," Kidd said today. "Usually, when you mix those two, you have to have something that confines it, in order to make it a dangerous product.

"I'll tell you, a lot of firefighters will use their number one tool, which is water, in a hazardous materials chemical situation like that, to cool the surrounding environments, to cool those other tanks, and to keep them from cooking off or exploding," he said.

Ammonium nitrate was used by Timothy McVeigh in the Oklahoma City bombing, which killed 168 and injured over 680 people. The bombing took place 18 years ago this week.

1:31 p.m. ET: The National Response Team of the Bureau of Alcohol, Tobacco, Firearms and Explosives, along with ATF special agents from the Houston Field Division, has been activated to join the investigation of the West Fertilizer Plant fire.

"This has been a week of loss and tragedy for the nation," Acting Special Agent in Charge of ATF Houston Field Division Crisanto Perez said today. "ATF is committed to working alongside state and local law enforcement by bringing its expertise to determine the origin and cause of this horrific incident. ATF will provide whatever resources necessary to thoroughly investigate and provide answers."

1:00 p.m. ET: Speaking at a press conference, Texas Gov. Rick Perry told reporters that the air, as well as the pipelines in the area, are being constantly monitored, and that gas distribution to homes has been disconnected. Gas connections will be double and triple checked before service is restored, Perry said.

Eric Gay/AP Photo

"Last night was truly a nightmare scenario for that community," Perry said. "West is a really small community. And just a few thousand people. Anyone who grew up in a small town like West, they know that this tragedy has most likely hit every family, and has touched practically everyone in that town. I ask all Texans and Americans to join me and [his wife] Anita in keeping them in our prayers."

12:40 p.m. ET: President Obama and lawmakers in Washington, D.C., expressed their condolences today, and pledged federal resources to help.

"Today our prayers go out to the people of West, Texas, in the aftermath of last night's deadly explosion at a fertilizer plant," Obama said in a written statement released to reporters. "A tight-knit community has been shaken, and good, hard-working people have lost their lives.

"I want to thank the first responders who worked tirelessly through the night to contain the situation and treat the wounded. My administration, through FEMA and other agencies, is in close contact with our state and local partners on the ground to make sure there are no unmet needs as search and rescue and response operations continue," Obama added.

11:40 a.m. ET: Speaking to reporters, Waco police spokesman Sgt. William Patrick Swanton said that more than 160 people have been injured, possibly more.

"I'd imagine that's increased at this point," he said.

Swanton also clarified that earlier reports of looting in the area were overestimated, and that there was only one instance of a looter.

"I have confirmed at least there was an incident last night when they thought they may have had a looter," he said. "It was an isolated incident."

Destruction in the area had varied, Swanton said.

"It ranges from broken windows to complete devastation. There are homes that are no longer homes … walls were ripped off, roofs were peeled back."

Swanton told reporters that the cool weather in the area has been helpful, but officials want to rescue survivors before rain increases.

"As the hours go by with the temp getting cooler, with rain here, we certainly want to find folks, if they're in the environment, injured. Numerous search teams are searching as rapidly as they can to save these people," he said.

10:31 a.m. ET: Aboard Air Force One en route to Boston, President Obama called Texas Gov. Rick Perry to offer any federal resources that may be needed to assist in the ongoing response-and-recovery effort.

9:45 a.m. ET: Sgt. William Patrick Swanton, spokesman for the Waco police, said at a press conference that one of the missing individuals has been found, a constable who is also a firefighter. He is currently hospitalized with "pretty serious injuries."

"We're still missing 3-4 firefighters," he said. "No police or EMS are missing, as far as I'm aware."

Swanton said that the "rough number" of fatalities remains at 5-15, but emphasized that it is still an estimate.

Swanton also said that a significant area of the fertilizer plant had been destroyed, and that homes were leveled as far as five blocks away.

"Homes have been destroyed. Part of that community is gone," he said.

A small amount of looting had been reported in the area, Swanton said. There are some unidentified people in the area.

"I can't tell you the number of looters or whether they have been caught … that is a significant concern for us," he said.

Authorities are now doing a more methodical search - under beds, in closets - and are still in search in rescue mode, and are not yet in recovery mode.

There is no word yet on the cause of the fire, Swanton said.

6:55 a.m. ET: An administration official tells ABC News that President Obama has been notified of the situation in Texas.

"The president has been notified. The administration is closely monitoring through FEMA who is also in contact with state and local officials who are responding," an official told ABC News in an email.

6:39 a.m. ET: West Mayor Tommy Muska said perhaps 60 homes have been damaged. All of the nursing home patients have been accounted for and all of downtown West, Texas, has been evacuated.

For those trying to locate their family members please call: 254-826-4115

6:30 a.m. ET: "Nightline" featured dramatic cellphone footage of the explosion. Residents said the explosion sounded like a "massive" bomb.

5:45 a.m. ET: Sgt. William Patrick Swanton of the Waco, Texas, Police Department estimated 5 to 15 fatalities from the fertilizer plant explosion. Swanton said 3 to 5 firefighters have been killed and there is also a law enforcement official who is unaccounted for.

5:23 a.m. ET: Pope Francis tweeted on his official Twitter account, "Please join me in praying for the victims of the explosion in Texas and their families."

"What you see with high level ammonia exposure is damage to your eyes, to your throat, to your nose, to your esophagus when you swallow," Besser told ABC News Radio. "A blast that's going in one direction, if you get a change in the wind, it can come to another neighborhood and be affected."

LM Otero/AP Photo

3:52 a.m. ET: ABC News has confirmed there are a total of 179 people hospitalized with 10 additional people in triage. At least 24 are in critical condition, nine of which are burn victims sent to Parkland Hospital in Dallas.

At least 38 people are in serious condition.

Hillcrest Baptist Medical Center in Waco: David Argueta, vice president of operations, says they currently have over 100 patients with lacerations, orthopedic and burn injuries. There are 12 people in surgery or have been admitted that are critical. More than 38 are seriously injured, but no fatalities have been reported.

Providence Healthcare Network in Waco: Spokesperson Heather Beck says they have currently treated 65 patients. Of the 65 patients, 12 have patients have broken bones, burns and head injuries. One patient is in critical condition.

3:38 a.m. ET: Sgt. William Patrick Swanton, spokesman for the Waco police expressed a concern of new explosions or leaks of ammonia from the plant's ruins.

2:58 a.m. ET: After hearing firefighters were down, George Willoughby, a police officer in a neighboring town, rushed to help the injured.

"I wasn't here (in West). I was in another town but yeah we felt up it (explosion) up there too," Willoughby told ABC News Radio.

2:45 a.m. ET: A team from the U.S. Chemical Safety Board (CSB) will be heading to the scene of the West Fertilizer Plant explosion, according to a CSB news release. They are expected to arrive Thursday afternoon.

2:24 a.m. ET: Jonnie Payne of Aderhold Funeral Home in West, Texas told ABC News that she has not "received any calls as of yet about fatalities." She said when the explosi0n happened her "whole house shook."

"My son went out there to check on what happened and was injured in the explosion. He's now in a hospital in Waco with a broken collarbone," she said.

2:10 a.m. ET: There are a total of 172 people confirmed hospitalized with 23 more people en route/to be admitted. At least 24 people are in critical condition and at least 38-40 people are in serious condition. Here is the breakdown from each area hospital:

Hillcrest Baptist Medical Center in Waco: Hospital officials said they have more than 100 patients - 101 registered but are currently assessing around 20 in triage area and are expecting another wave. They are seeing lots of patients with lacerations, orthopedic injuries and a few burns. Nine severely burned patients have been directly sent to Parkland hospital burn center in Dallas. They are reporting no fatalities.

Providence Healthcare Network in Waco: Hospital officials said they have treated 58 patients. They are in the process of triaging three. No word yet on whether they will get another wave, but are prepared. At least one patient is in critical condition Most of the injuries are moderate-broken bones, cuts, abrasions, scrapes, respiratory distress-most of these injuries were caused by flying glass or people knocked down by the force of the blast, according to hospital spokeswoman Heather Beck.

Hill Regional Hospital: Unclear

Parkland Hospital in Dallas:Hospital officials said they have nine severe burn patients.

Scott & White Memorial in Temple: Hospital officials said they received four patients, three at Scott & White Memorial Hospital, and one at McLane Children's Hospital. Another patient is in route to McLane Children's. At least two of the four patients are listed in critical condition at this time.

The Blood Donation Center will stay open until 2:30 a.m. to allow residents to come in and donate. The donors can get to the Blood Donation Center by coming in the main hospital entrance at 2401 S. 31 st Street, Temple.

Andy Bartee/AP Photo

2:03 a.m. ET: ABC News' Steve Osunsami is at a triage center in West, Texas: "As we drove into town we ran into firefighters who were getting gassed up outside of town who tell us the fire is still burning. It's under control. But it's still burning."

1:43 a.m. ET: West Mayor Tommy Muska said in a news conference said they are concerned about the wind - which they expect to change direction about 3 a.m.

Muska told residents to stay in inside because of the hydrous gas that is still in the air.

1:25 a.m. ET: The explosion registered as 2.1 magnitude quake according the USGS. Residents about 30 miles away in the town of Buffford told ABC News that they felt the quake.

AP Photo/Waco Tribune Herald, Rod Aydelotte

1:21 a.m. ET: VIDEO: Homes and business were completely destroyed around the West, Texas, fertilizer plant.

1:09 a.m. ET: Texas Department of Public Safety trooper D.L. Wilson said in a short news conference that there are more than 100 injuries with fatalities confirmed but did not specify how many deaths. Officials are searching for more people and are doing a house by house search. About 133 people were evacuated from a nursing home. About half the town has been evacuated. Between 50-75 buildings were destroyed or damaged.

"Massive. Just like Iraq. Just like the Murray Building in Oklahoma City… So you can imagine what kind of damage we're looking at," Wilson said in describing the blast.

12:53 a.m. ET: Blood drives are planned for Thursday in Texas. Linda Goelzer of Carter Blood Care, the primary blood support service supporting more 58 counties, largest blood provider in Texas told ABC News the people in the community of West are "heart of gold people, like a Norman Rockwell painting."

"The whole town is being evacuated. We had our blood supply pretty well stocked in Waco as of today but now we are sending more than 300 units of blood from Dallas Fort Worth down to Waco, that's where patients are going. Many are being care-flighted to Parkland Hospital in Dallas for treatment at their burn center," Goelzer said.

"Tonight our message to our donors is don't everybody come at once, we will have patients for who knows how long who will be needing blood. Especially O-negative are needed, universal donor, will likely be expended tonight. What we tell people is that the blood helping people tonight is what's already on the shelves. What we'll need most is for consistency. We have blood drives everyday and we will have them tomorrow, we just don't want people flooding in, in droves, like they did after 9/11. We're asking our regular donors to keep coming throughout the week because we expect there will be many survivors."

12:33 a.m. ET: At least 124 people hospitalized, with one hospital telling us that 20 more are on the way. Of those, 38 considered serious.

AP Photo/Michael Ainsworth/The Dallas Morning News

12:19 a.m. ET: According to the CEO of the Providence Healthcare Network, Brett Esrock (in Waco), says officials are triaging the wounded. Hillcrest Baptist Medical Center has treated, or is treating 29 wounded, mostly minor to moderate injuries: cuts abrasions, broken bones, respiratory distress, and one critical injury. Hospital officials are being told they are about to receive an additional 20 patients "they are coming in ambulances cars vans, pretty much anything." Other wounded people are also being sent to Hillsboro Regional Hospital, which has apparently received another 60 patients. - Matt Gutman

11:48 p.m. ET: West City Hall suffered significant damage according to Gail Scarborough with Texas Department of Public Safety. The middle school also caught on fire due to a gas leak in the building.

11:00 p.m. ET: Texas Gov. Rick Perry released the following statement on the explosion in West, Texas: "We are monitoring developments and gathering information as details continue to emerge about this incident. We have also mobilized state resources to help local authorities. Our thoughts and prayers are with the people of West, and the first responders on the scene."